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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – July 11th and 12th, 2018

This content was originally published by the Longmont Observer and is licensed under a Creative Commons license.

Forecast discussion:

Note: I'm nearing the end of my two week family camping trip.  My available bandwidth is very low so I'm keeping posts shorter than normal and less graphically intensive.

We are clearly in the where's-the-monsoon-moisture? time of year.  The giant upper air ridge and high center (Figure 1) are parked almost on top of Longmont Tuesday.  It won't move far by Wednesday, explaining the 100°F + temperatures. Remember, we average one 100°F + day every other year... so we've really hit the heat hard this year so far.  I've indicated the tropical moisture flow as dark green arrows.  The circulation around the high is pushing it all to the south and up into the west and over us to the north.

This high is also stirring the smoke from various Western U.S. fires making the skies mildly milky.  This probably won't clear out in the near future.

You can see the above mentioned moisture as the grey and white colors in Figure 2 - the water vapor satellite image. The change that is coming over these two days comes from the high migrating eastward and the moisture plume bending eastward with it to give Colorado cooler temperatures and chances of thunderstorm rainfall.  Thursday and Friday will see a chance of storms statewide, but no severe weather is predicted at this time.

Figure 1: The 500mb upper air analysis for Tuesday PM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.

Figure 2: the water vapor satellite image from Tuesday PM. Reds/Oranges are dry air, greys/whites are moist air regions.

Figure 3: The forecast precipitation map from the GFS and NCEP for Friday morning.

The longer range forecast:

After cracking 100°F early week, we cool to around 90°F (just a bit above average) and thunderstorm chances return.  Saturday looks dry and hot again (as the plume moves east of us briefly) then the moisture rocks back to cover Colorado early next week.

Figure 4: the next 10 days of the graphical forecast for Longmont, CO from weatherunderground.com

Current Weather

Clear

Clear

43°F

UV Index
0 Low
Pressure
29.73 Rising
Visibility
10 miles
Dewpoint
22 °F
Humidity
43%
Wind
WSW 3.8 mph
Gust
8.9 mph
Wind Chill
41 °F

Hourly Forecast

Tomorrow
12 AM
40°F
Mostly clear
Tomorrow
1 AM
39°F
Mostly clear
Tomorrow
2 AM
38°F
Mostly clear
Tomorrow
3 AM
37°F
Mostly clear
Tomorrow
4 AM
36°F
Mostly clear
Tomorrow
5 AM
36°F
Partly cloudy
Tomorrow
6 AM
35°F
Partly sunny
Tomorrow
7 AM
37°F
Intermittent clouds
Tomorrow
8 AM
41°F
Intermittent clouds
Tomorrow
9 AM
45°F
Intermittent clouds
Tomorrow
10 AM
48°F
Intermittent clouds
Tomorrow
11 AM
51°F
Intermittent clouds

7 Day Forecast

Partly sunny w/ showers

Tuesday

60 °F

Times of clouds and sun with a couple of brief showers beginning at midday; windy


Partly cloudy

Tuesday Night

35 °F

Partly cloudy and colder; there can be frost in the normally colder spots


Intermittent clouds

Wednesday

58 °F

Cool with times of clouds and sun


Mostly cloudy w/ showers

Wednesday Night

39 °F

Increasing clouds with a shower in spots late


Intermittent clouds

Thursday

56 °F

Cool with times of clouds and sun


Partly cloudy

Thursday Night

40 °F

Partly cloudy


Mostly cloudy

Friday

63 °F

Mostly cloudy and warmer


Clear

Friday Night

42 °F

Clear


Mostly sunny

Saturday

68 °F

Mostly sunny


Mostly clear

Saturday Night

43 °F

Mainly clear


Sunrise and Sunset

Sunrise
5:52 AM
Sunset
8:02 PM

Based on AccuWeather data